A taller tire will give you taller gearing, but, in my opinion, just try it and then decide.I wouldn't be surprised if you feel it's just fine.

On my own WR250X, I used Michelin Pilot Power tires (it was a street bike for me) with 13/49 sprockets.I felt it was perfect for the bike.I did not measure or compare the circumference of the Pilot Powers to the original Bridgestone tires.